This invention relates to an integrated circuit card (hereinafter referred to as an IC card), and more particularly it relates to an IC card having improved resistance to flexing.
Conventional thin IC cards are made by laminating a plurality of rigid polyvinyl chloride sheets in the manner stipulated by JIS (Japan Industrial Standards) X6301. FIGS. 1 and 2 are cross-sectional views of two different conventional IC cards of the types of which the present invention relates.
The type of conventional IC card illustrated in FIG. 1 comprises a card body 1 and an IC module 4 which is housed inside the card body 1. The card body 1 has a laminated core 2 comprising four opaque core sheets 2a and two transparent overlays 3 on the top and bottom surfaces of the core 2. The core sheets 2a and the overlays 3 are laminated into a single body under heat and pressure. The card body 1 has a hole formed therein into which the IC module 4 is inserted. The dimensions of the hole are such that the top surface of the IC module 4, which has electrodes 5 formed thereon, is flush with the top surface of the card body 1. An unillustrated bonding agent is applied between the mutually contacting surfaces of the card body 1 and the IC module 4. A design is formed by silk screen printing or other means on the surfaces of the core sheets 2a which contact the transparent overlays 3.
The type of conventional IC card illustrated in FIG. 2 differs from that of FIG. 1 in that the IC module 4 is embedded inside the card body 1 and the top surface of the IC module 4 is partially covered by the top overlay 3. However, the structure of this type of IC card is otherwise identical to the IC card illustrated in FIG. 1.
The core sheets 2a and the overlays 3 of these conventional IC cards are generally made of rigid polyvinyl chloride sheets because, among other reasons, sheets of this type can be embossed with information such as the name and account number of the owner of the card. However, polyvinyl chloride sheets do not have good resistance to flexing. As the core sheets 2a are more flexible than the IC module 4 during bending of the IC card, stress concentrations develop in the regions 6 of the core sheets 2a near the corners of the bottom side of the IC module 4. When the IC is subjected to repeated bending, undesirable cracks often develop in these regions 6, sometimes resulting in the splitting of the IC card.